The present invention relates to drill chuck. More particularly this invention concerns a lockable chuck that can be tightened and loosened by hand.
A drill chuck as shown in commonly owned U.S. Pat. No. 5,82,761 has a body centered on and rotatable about an axis and formed with a plurality of angled guides opening axially forward at a front chuck end and holding respective radially displaceable jaws each formed with a row of teeth. A metallic inner ring axially fixed but rotatable about the axis on the body has a screwthread meshing with the teeth so that rotation of the inner ring displaces the jaws in their guides. An adjustment sleeve rotatable about the axis on the body has a hard outer part and an inner part of a softer material fixed on the outer part. A metallic intermediate ring fixed on the inner ring has formations coupled to the hard outer part. The inner part rides on the intermediate ring. The sleeve is provided with means for rotationally arresting the inner and intermediate rings on the body. In particular the plastic inner part is formed with a cam for actuating the arresting means.
Such a chuck has proven quite popular as it is easy to tighten and loosen by hand. It is, however, fairly complex.
It is therefore an object of the present invention to provide an improved lockable drill chuck.
Another object is the provision of such an improved lockable drill chuck which overcomes the above-given disadvantages, that is which has all the features of the above-described chuck but is of simpler construction.
A drill chuck has according to the invention a body centered on and rotatable about an axis, having a front part and a rear part, and formed with a plurality of angled guides opening axially forward at the front part. Respective jaws axially and radially displaceable in the guides are each formed with a row of teeth engaging an internal thread of a one-piece and unsplit tightening ring axially fixed but rotatable about the axis on the chuck-body front part and having an inner diameter greater than an outer diameter of the chuck-body front part. Thus rotation of the tightening ring displaces the jaws in their guides. A one-piece and unsplit snap ring set in the chuck-body rear part bears axially forward on the tightening ring, is formed with an array of outwardly projecting teeth, and has an inner diameter greater than the outer diameter of the chuck-body front part. An adjusts ment sleeve rotatable about the axis on the body has a front end with a surface bearing directly on the chuck-body front part. A coupling sleeve fixed to the tightening ring and engaging the adjustment sleeve has formations permitting limited relative angular movement of the adjustment sleeve relative to the tightening ring between a pair of end positions. A retaining member secures the adjustment sleeve on the chuck-body front end, and a locking element rotationally fixed to the adjustment sleeve is engaged between the teeth in one end position of the adjustment sleeve and disengaged from the teeth in the other end position of the adjustment sleeve.
Such a chuck can be assembled simply by fitting the parts axially together and finally fixing the adjustment sleeve in place with the retaining member. Since both the tightening ring and snap ring are annularly continuous, they are very strong. Thus the adjustment sleeve can be made of plastic or a nonmetallic material with no significant loss of durability on the part of the chuck. Machining the chuck body is substantially cheaper since, with the exception of the jaw passages, all its surfaces are surfaces of revolution so it can be turned.
According to the invention each passage has a front end and a rear end and the adjustment sleeve has an inner surface centered on the axis and engaging the chuck-body front part back to the rear passage ends. This construction improves the support of the adjustment sleeve on the chuck body and is made possible because the locking teeth are moved back into the body of the chuck, making the front end available for guiding purposes.
Furthermore in accordance with the invention the retaining member is formed by a radially deflectable tab on the adjustment sleeve. The chuck-body front end is formed with a radially outwardly open groove into which the tab can fit. For most efficient connection the adjustment sleeve is formed with a plurality of such tabs. Thus the adjustment sleeve can simply be snapped in place so the chuck can be assembled wholly without tools.
For further guiding of the adjustment member on the chuck body a disk fixed on the chuck-body rear part rearward of the tightening ring has an outer periphery engaging and guiding the adjustment sleeve. Snap-interfit formations between the disk and the chuck-body rear part secure the disk on the chuck-body rear part. More specifically the chuck-body rear part is formed with a rearwardly directed shoulder and immediately thereadjacent a radially outwardly open groove. The snap-interfit formations include a radially inwardly projecting ridge on the disk. The disk sitting on the shoulder is formed adjacent the ridge with axially throughgoing holes permitting an inner periphery of the disk to deform outward for fitting of the ridge to the groove. Thus the adjustment sleeve is supported at the extreme front end of the chuck directly on the chuck body and at the extreme rear end of the chuck on the disk fixed on the chuck body.
The snap ring according to the invention is formed with radially inwardly projecting tabs received in the passages. These tabs rotationally couple it to the chuck body. They also project axially forward and guidingly engage the respective jaws, making them move more smoothly.
The retaining member can also be a snap ring set in the chuck-body front part. This snap ring is split and of metal, although it would be possible to make it of an elastomer like rubber. The chuck-body front part has an extreme front end formed with chamfered edge facilitating installation of the snap ring, making it easy to fit the snap ring in place and complete the assembly of the chuck. It is further possible to provide the adjustment sleeve with an axially forwardly directed end shield cap, in particular when the adjustment sleeve is of plastic. This end shield cap can have an inner periphery engaged between the snap ring and the adjustment sleeve.